Dielectric composition and method of making same



M. BAER July 2', 1946A.

DIELECTRIC COMPOSITION AND METHOD OF MAKING SAME Filed June 18, 1943 .IZZO

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KPGE twink Q ll -10 0 K710730410 so 10 so I00 TEMP RATURE-m C I nvvzzvron M/LiS/MO B/IER l atenied Jul 2, i946 Application June lS, 1943, Serial No. 491,345

2 Claims. (01. 252-456) My invention relates to dielectric organic compounds and methods of making such compounds. Various halogenated organic compositions, such as chlorinated nephthalene and chlorinated diphenyl have been proposed as dielectrics for transformers, condensers and other electrical apparatus both for direct use in the form of liquid or-solid insulators surrounding the apparatus and contained in a suitable container and by using the liquid dilectrics to impregnate the porous spaces of another insulator r dielectric, in particular, a porous fibrous insulator, such as paper, fabrics or the like.

Whereas, chlorinated diphenyl as a dielectric has been successfully used in the past, other halogenated compounds, in particular, chlorinated naphthalenes have not been fully satisfactory due to their poor dielectric and other electrical properties.

Accordingly, an object of my invention is to provide an improved dielectric composition of the above characteristic and a method of preparing same.

A more specific object is to provide a new process of transformin chlorinated naphthalenes possessing poor dielectric and other electrical properties into compositions of high dielectric and other desirable characteristicsl On the accompanying drawing there are shown the improved characteristics of the novel dielectric compound obtained by the invention.

With the foregoing and other objects in view as will appear hereafter, the dielectric compound consistency of the resin obtained will vary from light mobile oils to viscous oils and to solids with increasing quantities of chlorides of sulphur used. A solid resin may also be obtained from an oily resin by removing any unreacted ehloronaphthalene by means ofvacuum or steam distillation or in any other suitable manner.

The success of the condensation depends main.-

ly on the choice of a proper catalyst. As pointed out, aluminum oxide has been found to be well suited for such a condensation.

When activated aluminum oxide is used as a catalyst, practically all the chlorine combined with the sulphur is eliminated as hydrogen chlo ride, the hydrogen being derived from those carbon hydrogen bonds which have been broken by the formation of the new carbon sulphur bond. The sulphur atom, therefore, joins two naphthyl chloride, groups with the formation of a sulphide or disulphide.

When catalysts other than aluminum oxides are used, part of the chlorine or the chlorides of sulphur enters the naphthalene nucleus, whereby to produce substitution products and some addition products which may be objectionable in certain cases because of their instability. Activated aluminum oxide as a catalyst has been found to eliminate all the chlorine of the chlorides of sulphur; A nearly theoretical amount of hydroge in Figures land 2 graphs illustrative of some of chloride is evolved during the reaction.

Other catalysts like aluminum, zinc, iron or chlorides or sulphides of these metals and other metals, while useful and effective, have been found to be less successful but other activated according to the invention consists substantially bleaching earths can be used with equal advanof a condensation product of chlorinated naphthalene, in particular of the lower chlorinated naphthalenes, and the chlorides of sulphur or i e depending on the circumstances and require ments.

By the process according to the invention, chlorinated naphthalenes possessing poor dielectric 0 properties are transformed into condensation the invention, the catalyst consists of activated 0 aluminum oxide.

- The condensation product or resin obtained in this manner has different consistencies depending on the ratio of chlorinated naphthalenes to chloride of sulphur used. If the amount of chlorinover a wide temperature range.

products or resins of good dielectric properties and other electrical characteristics. Some of the advantages obtained by the invention ar as follows: 1) High dielectric constant with relatively small variations within a wide temperature range. The dielectric constant observed by tests varied from 3.9 to 4.1 over a temperature range from 20 to 100 C. The dielectric constant at 25 C. of impregnated kraft paper was found to be about 5.2. (2) Low power factor of impregnated condensers According to practical tests, the power factor at 1000 cycles was found to range from .25% at room temperature to .5% at 95 C. (see Figure 2). (3) High insulation ated naphthalenes is maintained constant, the resistance found to be 6000 megohms per microiarad for a paper condenser 1 p p impregnated with the compound according employing krait to the invention. (4) High voltage breakdown found to be about 3800 volts D. C. for a condenser employing 3 layers of .0003" kraft paper and impregnated with the novel dielectric composition I according to the invention.

(5) Chemical stability. (6) No tendency towards crystallization.

(7) Non-inflammability.

The graphs shown in Figures 1 and 2 give a A more detailed, presentation of the changes in capacity and power factor, respectively, of a capacitor unit impregnated with the novel dielectric prepared in accordance with the invention.

The curves shown apply to a capacitor wound with three layers or .0003" kraft paper.

The following illustrates by way of example, a practical process for carrying out the invention.

1 The reagents used are: (1) 2.25 mols of monochloronaphthalene or a mixture of' chlorinated naphthalenes. (2) 1 mol of sulphur chloride.

(3) Amixtureof 40 and 80 mesh activated alu- In carrying out the process, 2.25 mols of dry monochloronaphthalene or a mixture of chlorinated naphthalenes, such as a mixture composed of 60% monochloronaphthalene, 30% dichloronaphthalene and 10% trichloronaphthalene are introduced into a flask or other suitable vessel. This material is heated to.70 C. and to it are added 50 grams of activated aluminum oxide. As soon as the latter has been introduced,

sulphur chloride is slowly added from a dropping funnel or in any other suitablemanner, while dition of sulphur chloride should be maintained The hydrogen chloride is no longer evolved- The reaction vessel must be fitted with a water cooled reflux condenser so as to run back into the reaction vessel any sulphur chloride or-chlorinated naphthalene which may have volatilized. Hydrogen chloride and a. small quantity of hydrogen sulphide are evolved during the condensation.

The resinous product obtained in this manner pended claims.

. mina (about 6% or less of the total'weights of the reagents).

. 4 is then thinned with and separated from the catalyst by filtration. The solution is then washed with water and neutralized. The solvent is steam distilled and the resin so obtained is freed from water by heating in vacuo. The final resin compound so obtained has a pale orange color and may be further improved, and purified by the use of .small quantities of activated alumina as an absorbing agent.

.While the invention has been described in terms of a specific embodiment it is to be understood'that it is of a broad applicationin that among others, various proportions of chlorinated naphthalenes and chlorides of sulphur may be used with equal advantage, the limits of the invention being defined by the scope of the ap- I claim: 1. A method of producing a dielectric which comprises heatinga mixture or 2.25 mols of dry monochloronaphthalene toabout "10 0., addin about .50 grams of activated aluminum oxide,

adding 1 mol oi. sulphur chloride at a constant rate while vigorously stirring the mass, raising thetemperature to about 90-95 C. and continuing stirring until hydrogen chloride is no longer evolved, thinning the resinous product obtained and separating it from the aluminum oxide by in vacuo.

I I the mass is stirred vigorously. The rate-of .ad-

v 2. A method of producing a dielectric which comprises treating a mixture of 2.25 mols of monochloronaphthalene, 30% dichloronaphthaconstant rate while vigorously stirring the mass,

raising the temperature to about -95 C. and

continuing stirring until hydrogen chloride isv no I longer evolved, thinning the resinous product obtained and separating it from the aluminum oxide by filtration, neutralizing and washing the solution wtih water, steam distilling the solvent and freeing the resin so obtained from water by heating in vacuo.

' MASSIMO BAER.

a solvent such as benzene 

